Low Volume‐Expansion, Insertion‐Type Layered Silicate Hierarchical Structure For Superior Storage Of Li, Na, K

Abstract

AbstractA hierarchical structure is successfully synthesized by coating polypyrrole (PPy) on the surface of carbon/saponite superlattice (denoted as PPy@C/SAP), and applied as low volume‐expansion insertion‐type anode for Li, Na, K storage.The synergistic effect of metal Ni, Fe doping, carbon/silicate superlattice, abundant oxygen vacancies and PPy coating leads to a good electronic conductivity and large current discharging capability. As a Si‐based material, PPy@C/SAP has excellent storage capability for Li (659 mAh g−1 after 1000 cycles at 2 A g−1 and 550 mAh g−1 after 1000 cycles at 5 A g−1), Na (maximum specific capacity of 533 and 327 mAh g−1 after 50 cycles) as well as K (236 mAh g−1 after 100 cycles). XPS, XANES, XRD, FTIR, HRTEM, SEM are used to detect the hybrid mechanism (bulk insertion and surface conversion) with a volume expansion as low as 9%. Insertion reaction driven by valence state change of Ni, Fe, Si (Ni0⇔Ni2+, Fe0⇔Fe3+, Si2+⇔Si4+) in laminates and conversion reactions between LiOH/Li2CO3 and LiH/Li2C2 catalyzed by Ni° contribute to the high performance. In the whole electrochemical process, layered structure is retained while the conversion reactions of LiOH (prodeced by laminates dehydroxylation) and Li2CO3 (electrolyte decomposition) cause the dynamic evolution of solid ectrolyte interphase. This study develops a promising Si‐based anode material for lithium ion batteries, sodium ion batteries and potassium ion batteries, which is significant for designing long cycle life rechargeable batteries.